A systematic search for the etiology of the sudden death in Cytoxan-treated Lagos bat virus-infected mice will be undertaken. A search in the medulla was negative for histopathologic lesions which might account for sudden death. In the absence of such a lesion, the working hypothesis is that mice die suddenly from a metabolic abnormality such as hypoglycemia or hyperkalemia. Serum electrolytes, pH. total protein, and glucose levels will be measured in Cytoxan-treated and untreated mice as well as in controls. Specific antibody is both protective and lethal to Lagos bat virus-infected mice depending on time of administration. Antibody preparations will be further fractionated to determine protective and lethal activites which will be characterized as to antibody type, avidity, and specificity.